CODEWITHSUNDEEP
mysqldockerdocker-compose
user3755946
user3755946

Reputation: 804

Why does my docker mysql database container refuse connection from my app(golang) container

When I run my docker app and type the following URLs I get the responses shown...

http://localhost:8080/complex

Hello...dial tcp 172.21.0.2:3306: connect: connection refused

I would have expected the connection to be accepted and then be able toe query the database etc.

If I deliberately change the connection string in my main.go file to a non existent host (added an x).

"root:root@tcp(godockerxDB:3306)/task_man")

Use this url...

http://localhost:8080/complex

I get this response...

Hello...dial tcp: lookup godockerxDB on 127.0.0.11:53: no such host

As I would expect, so the original host seems right but it is just refusing the connection.

I have connected to the db container manually and confirmed the database is there and setup correctly with the table and tasks and I am able to query the database form in there.

My main.go...

    package main

import (
    "database/sql"
    "encoding/json"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "github.com/gorilla/mux"
    "net/http"
)

func simple(w http.ResponseWriter, r *http.Request) {
    enableCors(&w)
    fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}

var db *sql.DB
var err error

func main() {
    fmt.Print("hello")
    router := mux.NewRouter()
    router.HandleFunc("/complex", complex).Methods("GET")
    router.HandleFunc("/text", simple).Methods("GET")
    err := http.ListenAndServe(":8080", router)
    fmt.Print(err)

}
func enableCors(w *http.ResponseWriter) {
    (*w).Header().Set("Access-Control-Allow-Origin", "*")
}
func complex(w http.ResponseWriter, r *http.Request) {
    enableCors(&w)
    fmt.Fprintf(w, "Hello...")
    db, err = sql.Open("mysql", "root:root@tcp(godockerDB:3306)/task_man")
    if err != nil {
        fmt.Fprintf(w, "Hello David")
        fmt.Fprintf(w, err.Error())
    }
    defer db.Close()
    err2 := db.Ping()


    fmt.Fprintf(w, err2.Error())
}

My App Docker File...

> FROM golang:1.12-alpine
> 
> RUN apk add --no-cache git
> 
> # Set the Current Working Directory inside the container WORKDIR /app/godocker
> 
> 
> COPY go.mod . COPY go.sum .
> 
> RUN go mod download
> 
> COPY . .
> 
> # Build the Go app RUN go build -o ./out/godocker .
> 
> 
> # This container exposes port 8080  EXPOSE 8080
> 
> # Run the binary program produced by `go install` CMD ["./out/godocker"]

My db Dockerfile...

FROM mysql:5.7
ENV MYSQL_ROOT_PASSWORD=root
COPY setup.sql /docker-entrypoint-initdb.d/

My docker-compose.yml ...

# Use root/example as user/password credentials
version: '3.1'

services:
  app:
    build:
      context: ./
      dockerfile: Dockerfile
    container_name: godockerAPP
    ports:
      - "8080:8080"
    depends_on:
      - db      
    restart: always
  db:
    build:
      context: ./dockerfiles/db
      dockerfile: Dockerfile
    container_name: godockerDB
    command: --default-authentication-plugin=mysql_native_password
    ports:
      - "3306:3306"
    restart: always

The command I run to spin up the docker compose...

docker-compose down
docker-compose build
docker-compose up -d

Building db Step 1/3 : FROM mysql:5.7 ---> 718a6da099d8 Step 2/3 : ENV MYSQL_ROOT_PASSWORD=root ---> Using cache ---> 9087b3db47ac Step 3/3 : COPY setup.sql /docker-entrypoint-initdb.d/ ---> Using cache ---> 195614e33d96 Successfully built 195614e33d96 Successfully tagged godocker_db:latest Building app Step 1/11 : FROM golang:1.12 ---> ffcaee6f7d8b Step 2/11 : ENV GO111MODULE=on ---> Using cache ---> 25377bdeb7af Step 3/11 : ENV CGO_ENABLED=0 ---> Using cache ---> fd86c2a9948c Step 4/11 : WORKDIR /app/server ---> Using cache ---> 8d59571272b7 Step 5/11 : COPY go.mod . ---> Using cache ---> d1c8a0f00d33 Step 6/11 : COPY go.sum . ---> Using cache ---> a1b4b294de83 Step 7/11 : RUN go mod download ---> Using cache ---> 803fd4244374 Step 8/11 : COPY . . ---> 37887395cadd Step 9/11 : RUN go build -o main . ---> Running in efe19e8eedc8 Removing intermediate container efe19e8eedc8 ---> a115e9f17fc3 Step 10/11 : EXPOSE 8080:8080 ---> Running in 4155040d490c Removing intermediate container 4155040d490c ---> 3e431bff9e84 Step 11/11 : CMD ["./main"] ---> Running in f5f9bab56ab0 Removing intermediate container f5f9bab56ab0 ---> a8867809f163 Successfully built a8867809f163 Successfully tagged godocker_app:latest

C:\DEV\Go\src\godocker>docker-compose up -d Creating network "godocker_default" with the default driver Creating godockerDB ... done Creating godockerAPP ... done

C:\DEV\Go\src\godocker>dow e03697533be6 239278c1f0ea

C:\DEV\Go\src\godocker>dup

C:\DEV\Go\src\godocker>docker-compose down Removing godockerAPP ... done Removing godockerDB ... done Removing network godocker_default

C:\DEV\Go\src\godocker>docker-compose build Building db Step 1/3 : FROM mysql:5.7 ---> 718a6da099d8 Step 2/3 : ENV MYSQL_ROOT_PASSWORD=root ---> Using cache ---> 9087b3db47ac Step 3/3 : COPY setup.sql /docker-entrypoint-initdb.d/ ---> Using cache ---> 195614e33d96 Successfully built 195614e33d96 Successfully tagged godocker_db:latest Building app Step 1/11 : FROM golang:1.12 ---> ffcaee6f7d8b Step 2/11 : ENV GO111MODULE=on ---> Using cache ---> 25377bdeb7af Step 3/11 : ENV CGO_ENABLED=0 ---> Using cache ---> fd86c2a9948c Step 4/11 : WORKDIR /app/server ---> Using cache ---> 8d59571272b7 Step 5/11 : COPY go.mod . ---> Using cache ---> d1c8a0f00d33 Step 6/11 : COPY go.sum . ---> Using cache ---> a1b4b294de83 Step 7/11 : RUN go mod download ---> Using cache ---> 803fd4244374 Step 8/11 : COPY . . ---> 05a487690611 Step 9/11 : RUN go build -o main . ---> Running in 9d9cc6a3b214 Removing intermediate container 9d9cc6a3b214 ---> ee950a1706f5 Step 10/11 : EXPOSE 8080:8080 ---> Running in faa43abcfe40 Removing intermediate container faa43abcfe40 ---> 877be92dc560 Step 11/11 : CMD ["./main"] ---> Running in dd2dcf9ce4be Removing intermediate container dd2dcf9ce4be ---> cf9bea6d2348 Successfully built cf9bea6d2348 Successfully tagged godocker_app:latest

C:\DEV\Go\src\godocker>docker-compose up -d Creating network "godocker_default" with the default driver Creating godockerDB ... done Creating godockerAPP ... done

C:\DEV\Go\src\godocker>dow d56302aeb09b 0cef3117aac8

C:\DEV\Go\src\godocker>dup

C:\DEV\Go\src\godocker>docker-compose down Removing godockerAPP ... done Removing godockerDB ... done Removing network godocker_default

C:\DEV\Go\src\godocker>docker-compose build Building db Step 1/3 : FROM mysql:5.7 ---> 718a6da099d8 Step 2/3 : ENV MYSQL_ROOT_PASSWORD=root ---> Using cache ---> 9087b3db47ac Step 3/3 : COPY setup.sql /docker-entrypoint-initdb.d/ ---> Using cache ---> 195614e33d96 Successfully built 195614e33d96 Successfully tagged godocker_db:latest Building app Step 1/11 : FROM golang:1.12 ---> ffcaee6f7d8b Step 2/11 : ENV GO111MODULE=on ---> Using cache ---> 25377bdeb7af Step 3/11 : ENV CGO_ENABLED=0 ---> Using cache ---> fd86c2a9948c Step 4/11 : WORKDIR /app/server ---> Using cache ---> 8d59571272b7 Step 5/11 : COPY go.mod . ---> Using cache ---> d1c8a0f00d33 Step 6/11 : COPY go.sum . ---> Using cache ---> a1b4b294de83 Step 7/11 : RUN go mod download ---> Using cache ---> 803fd4244374 Step 8/11 : COPY . . ---> 8a1880bb8b56 Step 9/11 : RUN go build -o main . ---> Running in 84f20ebb4606 Removing intermediate container 84f20ebb4606 ---> e0304d6454d4 Step 10/11 : EXPOSE 8080:8080 ---> Running in 7a0b6392be6e Removing intermediate container 7a0b6392be6e ---> 3b18860bca2c Step 11/11 : CMD ["./main"] ---> Running in 018d6769b721 Removing intermediate container 018d6769b721 ---> bbf448ab621c Successfully built bbf448ab621c Successfully tagged godocker_app:latest

C:\DEV\Go\src\godocker>docker-compose up -d Creating network "godocker_default" with the default driver Creating godockerDB ... done Creating godockerAPP ... done

Upvotes: 0

Views: 958

Answers (1)

Cyril G.
Cyril G.

Reputation: 2017

To connect, you have to use the service name declared in your docker-compose.yml instead of container name.

db:3306 // instead of godockerDB:3306

Upvotes: 1

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